For certain purposes it is necessary to place on a continuous strip of web material, such as paper, one or more bands of a liquid coating material in thin layers running lengthwise of the strip and spaced laterally across the strip. The coating material may be, e.g., a plastic or polymer material in a melt form, but is more usually provided in solution or dispersion in water or other fairly volatile solvent.
In the past it has been customary to print such material on the web, as by employing a rotating roller or multiple rollers. These rollers can be ridged or grooved to produce the separate bands. However, the bands produced in this way are often somewhat non-uniform, both as to thickness of material application and as to straightness of the edges. Further, only certain limited viscosities of coating material solution or melt have been usable. A too-thin composition, for example, tends to be spattered by the rotating roll. Cylindrical coating heads demand a high viscosity solution (e.g. 5000 cp) if the application is to be limited to discrete bands; lower viscosities will permit the solution to flood the entire cylinder.
Accordingly, it is desirable that there be provided apparatus and method with which a moving web of material such as paper can be coated in a manner overcoming the problems and limitations described aforesaid.